This invention relates to a process for the production of a spun-fiber web from filaments of a synthetic polymer wherein the filaments exit through spinnerets from a molten mass of synthetic polymer and are guided through a cooling well traversed by cooling air and, after cooling and strengthening, are seized mechanically by means of at least one take-off roll and are conducted over a portion of a surface of at least one takeoff roll, and thereafter the filaments are swirled and deposited to form the web on a depositing conveyor belt.
The invention furthermore concerns an apparatus for producing spun-fiber webs from filaments of a synthetic polymer exiting from a molten mass of synthetic polymer through spinnerets and being taken off mechanically, with an extruder for melting the synthetic polymer comprising a die head having a plurality of spinnerets for delivery of the filaments and with a cooling well adjoining the spinnerets and supplying air for cooling the filaments, a mechanical take-off device downstream of the cooling well with at least one take-off roll for taking off the filaments from the spinnerets, and a unit for forming the web in random array of the filaments, with an air-traversed diffuser and a perforated depositing conveyor belt with a suction unit.
Processes are known for the production of spun-fiber non-woven fabrics of stretched filaments made of synthetic polymers wherein the filaments are taken off the spinnerets from the melt either mechanically or aerodynamically and are subsequently additionally stretched in the strengthened condition.
In the reshaping of thermoplastic synthetic resins, a distinction is made between cold reshaping and hot reshaping. In case of amorphous thermoplastics the cold reshaping takes place below the glass transition temperature; in this connection, amorphous thermoplastics can be cold-formed and stretched only within limits. Partially crystalline thermoplastics are coldformed below their crystallite melting range and above their yield point, particularly stretched. Hot-forming takes place in case of amorphous thermoplastics above their softening temperature range in the thermoelastic state range; whereas partially crystalline synthetic resins can be thermoformed and stretched to a limited extent above their crystallite melting range and below the molten condition. All hot-forming processes are anisotropic and must be frozen in by cooling under tension up to a sufficient extent below the glass transition temperature and, respectively, the crystallite melting range.
In the process known from DOS 3,117,737 for the production of spun-fiber webs, the filaments, exiting from a molten thermoplastic mass out of the spinnerets and directly entering into a cooling chamber, are quenched and subsequently aerodynamically taken off the spinnerets by means of the flowing coolant and are stretched along the lines of a cold-forming operation. The drawing of the filaments as well as the stretching step take place aerodynamically, and the stretching step is conducted in the strengthened condition of the filaments. German Patent 3,400,847 likewise discloses a process for producing a spun-fiber fleece from stretched filaments of a thermoplastic synthetic resin by means of aerodynamic stretching of the filaments, taken off aerodynamically from a melt, in the strengthened, cooled condition.
U.S. Pat. No. 3,338,992 describes a process for the manufacture of a spun-fiber non-woven fabric from stretched filaments of thermoplastic synthetic resins wherein the filaments exiting from the spinneret are cooled and bonded and subsequently mechanically taken off and stretched by reheating to stretching temperatures below the crystallite melting zone mechanically by means of rolls. In contrast to the methods known from DOS 3,117,737 and German Patent 3,400,847 operating with aerodynamic treatment of the filaments, the process in U.S. Pat. No. 3,338,992 employs mechanical action upon the filaments, stretching being carried out as a cold-shaping of the filaments.
A process for the production of a spun-fiber web of filaments made of thermoplastic polymer is known from U.S. Pat. No. 3,509,009 wherein the filaments exit from the melt through spinnerets into a cooling shaft exposed to cooling air, and the filaments are drawn therefrom in aerodynamic fashion. Additionally, in this process, the filaments are exposed to hot air immediately after leaving the spinnerets in order to attain a reduction in cross section of the filaments in the molten condition of the polymer after exiting from the spinnerets by means of the subsequent aerodynamic take-off step in the cooling shaft. In this method, due to the additional injection of hot air, there is the danger of having the filaments exiting from the spinnerets stick to one another.
German Patent 3,603,814 discloses a process and apparatus for the production of a spun-fiber fleece from stretched filaments of a synthetic polymer wherein the filaments, leaving the spinnerets in the molten condition, are taken off mechanically from the spinneret and are subsequently stretched mechanically in the cold-reshaping zone before they are deposited in random array into a web and then bonded.